Studies of jet fuel thermal stability, oxidation and additives using the quartz crystal microbalance and oxygen monitoring

The Quartz Crystal Microbalance (QCM) with oxygen sensor and pressure transducer is a novel test technique that allows for the in situ, real-time analysis of jet fuel thermal and oxidative stability. Thermal stability refers to the deposit-forming tendency of a fuel. Oxidative stability refers to the rate at which oxygen is consumed. The QCM offers the unique advantage of measuring very small amounts of surface deposition, on the order of 100 nanograms/cm{dollar}sp2{dollar}, with the simultaneous measurement of oxidation by monitoring oxygen consumption.; The autoxidation chain mechanism is used to model oxidation and deposition of fuels at ambient and elevated temperatures. While oxidizing to form deposits, sulfur and nitrogen containing compounds with weakly bound hydrogen atoms can interfere with the major chain autoxidation mechanism resulting in a decrease in the rate of oxidation. Fuels that lack these molecules oxidize rapidly and exhibit low deposition. Many fuels demonstrate this inverse relationship between oxidative and thermal stability.; Oxygen studies show that deposition does not necessarily increase with increased oxygen availability. Under partial oxygen consumption conditions, a lower oxygen availability may result in higher deposition. Studies with two different fuels show that there exists a temperature at which deposition is a maximum, above and below which deposition decreases.; Materials studies were performed using gold, aluminum, platinum and silver crystal electrodes acquired from the manufacturer. Aluminum and gold show similar results. Since aluminum is a material found in jet fuel systems, this study confirmed the viable use of gold crystals in jet thermal stability studies. Platinum exhibits catalytic behavior in one of the fuels tested. A series of studies reveal that the silver crystal electrode reacts with elemental sulfur in jet fuel to form a silver sulfide tarnish on the electrode surface. (Abstract shortened by UMI.)...